Place large saucepan over medium heat and add oil and bay leaf.
Once oil is hot add onion and ginger with kosher salt.
Add mustard seeds, cumin, and turmeric and mix onion, continuing to saute it until it is clear and begins to caramelize.
Mix in cauliflower and allow to saute slightly, for 2-3 minutes, then add in chicken stock and split peas. Add enough water up to the level of the split peas and cauliflower.
Bring to a boil, then bring down heat to simmer.
Add sugar, chilli powder, coriander, vinegar, and and cover.
Allow to simmer for 1-2 hours, mixing frequently. Soup is cooked adequately when cauliflower and split peas have broken down completely and combination resembles oatmeal consistency.
Puree well in blender, then may return to heat to simmer until serving time.
Salt before serving.
Note, soup will be concentrated and thick, which makes it good to store in separate containers and add water prior to reheating. If soup is too thick for desired consistency, may add water and mix gently prior to heating.